Philip C. Stevenson

Bio: Philip C. Stevenson is an academic researcher from Royal Botanic Gardens. The author has contributed to research in topics: Nectar & Pollinator. The author has an hindex of 41, co-authored 161 publications receiving 4891 citations. Previous affiliations of Philip C. Stevenson include Birkbeck, University of London & University of Greenwich.

Caffeine in Floral Nectar Enhances a Pollinator's Memory of Reward

Abstract: Plant defense compounds occur in floral nectar, but their ecological role is not well understood We provide evidence that plant compounds pharmacologically alter pollinator behavior by enhancing their memory of reward Honeybees rewarded with caffeine, which occurs naturally in nectar of Coffea and Citrus species, were three times as likely to remember a learned floral scent as were honeybees rewarded with sucrose alone Caffeine potentiated responses of mushroom body neurons involved in olfactory learning and memory by acting as an adenosine receptor antagonist Caffeine concentrations in nectar did not exceed the bees' bitter taste threshold, implying that pollinators impose selection for nectar that is pharmacologically active but not repellent By using a drug to enhance memories of reward, plants secure pollinator fidelity and improve reproductive success

Plant secondary metabolites in nectar: impacts on pollinators and ecological functions

Abstract: 1. The ecological function of secondary metabolites in plant defence, against herbivores is well established, but their role in plant-pollinator interactions is less obvious. Nectar is the major reward for pollinators, so the occurrence of defence compounds in the nectar of many species is unexpected. However, increasing evidence supports a variety of potential benefits for both plant and pollinator from these components. 2. Secondary metabolites in nectar can be toxic or repellent to flower visitors, but they can also go undetected or make nectar attractive . For example, caffeine in nectar improves pollinator memory for cues associated with food rewards and enhances pollen transfer. All of these effects depend on the concentration of nectar metabolites so should be evaluated experimentally at a range of ecologically relevant doses. 3. Beneficial effects may include the following: a) increasing specialization in plant-pollinator interactions, b) protecting nectar from robbery or larceny, and c) preservation of nutrients in nectar from microbial degradation and reducing microbial disease levels in flower visitors. 4. This review synthesises evidence from recent literature that supports selection for secondary metabolites in floral nectar as an adaptation that drives the co-evolution between plants and their pollinators. However, their presence in nectar could simply be a consequence of their occurrence elsewhere in the plant for defence (pleiotropy). We draw attention to the need for studies demonstrating benefits to the plant, the importance of levels of exposure and a effects on target species beyond the current emphasis on alkaloids and bees.

Heliothis/ helicoverpa management: emerging trends and strategies for future research

Abstract: The cotton bollworm/corn earworm/legume pod borer (Heliothis/Helicoverpa) are the most important constraints to increase the production and productivity of crops worldwide (Hardwick 1970; Fitt 1989). These pests damage a wide range of economically important crops including cotton, chickpea, pigeonpea, maize, peas, cowpea, sunflower, sorghum, groundnut, field beans, tobacco, a range of vegetables, fruit crops and tree species.

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

Modern Applied Statistics With S

Abstract: Thank you very much for downloading modern applied statistics with s. As you may know, people have search hundreds times for their favorite readings like this modern applied statistics with s, but end up in harmful downloads. Rather than reading a good book with a cup of coffee in the afternoon, instead they cope with some harmful virus inside their laptop. modern applied statistics with s is available in our digital library an online access to it is set as public so you can download it instantly. Our digital library saves in multiple countries, allowing you to get the most less latency time to download any of our books like this one. Kindly say, the modern applied statistics with s is universally compatible with any devices to read.

Botanical insecticides, deterrents, and repellents in modern agriculture and an increasingly regulated world

Abstract: Botanical insecticides have long been touted as attractive alternatives to synthetic chemical insecticides for pest management because botanicals reputedly pose little threat to the environment or to human health. The body of scientific literature documenting bioactivity of plant derivatives to arthropod pests continues to expand, yet only a handful of botanicals are currently used in agriculture in the industrialized world, and there are few prospects for commercial development of new botanical products. Pyrethrum and neem are well established commercially, pesticides based on plant essential oils have recently entered the marketplace, and the use of rotenone appears to be waning. A number of plant substances have been considered for use as insect antifeedants or repellents, but apart from some natural mosquito repellents, little commercial success has ensued for plant substances that modify arthropod behavior. Several factors appear to limit the success of botanicals, most notably regulatory barriers and the availability of competing products (newer synthetics, fermentation products, microbials) that are cost-effective and relatively safe compared with their predecessors. In the context of agricultural pest management, botanical insecticides are best suited for use in organic food production in industrialized countries but can play a much greater role in the production and postharvest protection of food in developing countries.

Bee declines driven by combined stress from parasites, pesticides, and lack of flowers

Abstract: Bees are subject to numerous pressures in the modern world. The abundance and diversity of flowers has declined, bees are chronically exposed to cocktails of agrochemicals, and they are simultaneously exposed to novel parasites accidentally spread by humans. Climate change is likely to exacerbate these problems in the future. Stressors do not act in isolation; for example pesticide exposure can impair both detoxification mechanisms and immune responses, rendering bees more susceptible to parasites. It seems certain that chronic exposure to multiple, interacting stressors is driving honey bee colony losses and declines of wild pollinators, but such interactions are not addressed by current regulatory procedures and studying these interactions experimentally poses a major challenge. In the meantime, taking steps to reduce stress on bees would seem prudent; incorporating flower-rich habitat into farmland, reducing pesticide use through adopting more sustainable farming methods, and enforcing effective quarantine measures on bee movements are all practical measures that should be adopted. Effective monitoring of wild pollinator populations is urgently needed to inform management strategies into the future.